It is an important technique for products such as cosmetics and perfumes to stably incorporate hydrophobic substances such as oils as emulsions. In general, an emulsion making use of a low molecular surfactant is relatively stable as emulsified particles are small, but the emulsified particles are so small that oiliness is felt when applied to the skin. An emulsion making use of a high molecular compound, on-the other hand, provides relatively large particles and is excellent to the feel of the skin when applied, but it is accompanied by a drawback that the emulsion is less stable. JP-A-59-0098727 discloses a process for preparing a stable emulsion by mixing an oil component with a glycopeptide and a polyhydric alcohol and diluting the resultant mixture with water to reduce the particle size. As the resulting emulsified particles are small in size, there remains the drawback of the inherent oily feeling of the emulsion upon application.
On the other hand, in a solution system containing a large amount of surfactant, such as in a detergent, even an emulsion having a small emulsified particle size which is considered to be stable may lose its stability, and the emulsified state is thus broken. Even when a hydrophobic substance useful for washing surfaces of the skin or hair is added as an emulsion, the hydrophobic substance is emulsified by a surfactant employed as a detergent so that the forming property of the detergent deteriorates. Further, the hydrophobic substance, despite its additional incorporation, is emulsified by the surfactant used as the detergent in such a case. Most of the hydrophobic substance so added is, therefore, washed off, leading to a problem that it is very difficult to make the hydrophobic substance remain on the washed surface after use.
An object of the present invention is, therefore, to provide an o/w emulsion which is stable even in a system having a large amount of a surfactant, as in a detergent, that is, excellent in resistance to surfactant solutions which can be added to detergents without impairing its basic performance such as foaming and excellent to the feel of the skin when applied, and also a preparation process of the same.